DE102006062376B4 - Method and display device for reducing speckle - Google Patents

Abstract

Method for reducing speckle of a three-dimensional holographic reconstruction generated in a holographic reproduction device, in which a controllable light modulator (SLM) in which a hologram of a 3D scene is coded is illuminated by sufficiently coherent light, in which a reconstruction optics (RO ) spatially modulated light within a viewer's space in an eye position, which is located in a rear focal plane of the reconstruction optics (RO), transformed and reconstructed in a reconstruction space the 3D scene and - in which the illumination is controlled by a control means (CM) characterized in that the control means (CM) influences the coherent light in at least one property such that a plurality of complex-valued wavefronts having slightly different wavelengths relative to each other within the range of a few nanometers pass through the light modulator (SLM) modulating with coded hologram values rt, and the modulated complex wavefronts are transformed by the reconstruction optics (RO) into the eye position (PE) and in the reconstruction space between the eye position (PE) and the light modulator (SLM) at the same location several reconstructions of the same 3D scene with each other produce different speckle patterns which are seen from the eye position (PE) from the respective eye of the observer averaged as a single speckle reduced reconstruction (RE) of the 3D scene.

Description

The invention relates to a method for reducing speckle patterns of a three-dimensional holographic reconstruction of a three-dimensional scene and a holographic display device for carrying out the method.

Fields of application of the invention are methods with which the storage and reconstruction of complex wavefronts of a three-dimensional scene (3D scene) by holography using preferably laser light in real time or near real time in holographic playback devices and in which the reconstruction can be seen from a virtual viewer window ,

Holography enables the recording and the optical reproduction of a three-dimensional object or a moving 3D scene with wave-optical methods. The 3D scene is encoded in a light modulator that serves as the carrier medium. As a result of the illumination with interference-capable light waves, each point of the encoded 3D scene forms a starting point of light waves that interfere with each other and spatially reconstruct the 3D scene as resulting light wave front, as if it were caused by a light propagation from the actual object in space. The holographic reconstruction of the object or of the 3D scene preferably takes place with a projection device and / or a reconstruction optical unit by illuminating the carrier medium with normally sufficiently coherent light.

In the document, the 3D scene is reconstructed in a holographic display with a viewer window, here a visibility area in a periodicity interval of the complex-valued wavefront in the back focal plane of a reconstruction means in a viewer space. From the observer window, a right or left eye of a viewer sees the reconstruction of the 3D scene. In this case, the observer window is preset in size in front of a reproduction means and generally corresponds at least to the size of an eye pupil.

Viewed wave optically, the viewer window is formed either as the direct or inverse Fourier transform or Fresnel transform of a hologram encoded in a carrier medium or as the image of a wavefront encoded in a carrier medium in a viewer space, the viewer window comprising only a single diffraction order of a periodic reconstruction , The hologram or the wavefront are calculated from the 3D scene in such a way that within the one diffraction order used as the visibility region, any crosstalk of other diffraction orders into the viewer window, which usually occurs in reconstructions using light modulators, is prevented. Combined with an arrangement or a method for suppressing higher orders of diffraction, it is thus possible, in the multiplex method, successively to represent a left and right eye of a viewer without crosstalk 3D scenes. Likewise, a multiplex method for several people is only possible.

Spatial light modulators such as LCD, LCoS, etc., which modulate the phase and / or the amplitude of the incident light, serve as carrier or recording media for holograms or complex-valued wavefronts of a 3D scene. To be able to display moving 3D scenes, however, the refresh rate of the carrier medium must be sufficiently large. The values coded in the carrier medium in regularly arranged pixels can originate from a real object or be a computer-generated hologram (CGH).

Viewing the reconstruction of the 3D scene can be done by the viewer looking directly at the carrier medium. This is referred to in this document as a direct view setup. Alternatively, the viewer can look at a screen onto which either an image or a transform of the values coded in the carrier medium is projected. This is called projection construction in this document. In the following, the designation screen is used both for the screen in the projection setup and for the carrier medium in the direct-view setup.

Due to the discrete recording, the reconstruction of the hologram is only possible within a periodicity interval of the reconstruction of a wavefront given by the resolution of the carrier medium, as a result of diffraction. In the adjacent periodicity intervals, the reconstruction is repeated, usually with disturbances.

The use of coherent laser light to illuminate a light modulator creates disturbing patterns, which are known as speckle pattern or granulation. This is understood to mean a granulation-like interference pattern that results from the interference of many light waves with statistically irregularly distributed phase differences.

When reconstructing a hologram, the speckle patterns are detrimental. Normally, the hologram calculation is preceded by a discrete sampling of the 3D scene, since only a discrete recording is possible on the carrier medium. Certain coding methods in which the information about the 3D scene is suitably incorporated in the Carrier medium is stored, allow in principle a reconstruction in which at the location of the sampling points even the reconstruction completely coincides with the scanned object. However, the physical reconstruction again results in a continuous course between the sampling points. There are deviations from the intensity curve in the object, whereby the reconstruction contains speckle patterns that reduce the quality of the reconstruction. This is the case, in particular, if the calculation of the hologram is carried out with a random phase of the object points, which however is advantageous for certain other reasons.

Reduction of the speckle patterns in the reconstruction of the 3D scene can in principle be achieved by temporal and / or spatial averaging, wherein the reconstruction is generated from values of a 3D scene coded into an external medium or from appropriately calculated hologram values. In doing so, the eye of the beholder always averages several reconstructions with different speckle patterns that are shown to him, whereby a reduction of this disturbance is perceived. For example, in the DE 195 41 071 A1 to time the granulation in a hologram test, a rotating rectangular glass plate brought into the beam path. It rotates with a tuned to the frequency of a detector frequency, causing the speckle no longer disturbing. However, such a method can only be used to reduce a two-dimensional, planar speckle pattern, with the lens being in the plane of the speckle pattern. For the time averaging for reducing speckle patterns of a 3D scene, it is known to calculate the 3D scene with a predetermined number of different random phases and to display the corresponding holograms in quick succession on a carrier medium. Due to the multiple hologram calculations, however, the computing power increases significantly and the refresh rate of the carrier medium in the representation of the holograms would have to increase sharply in an undesired manner.

Furthermore, it is generally known from the literature for spatial averaging to subdivide a carrier medium into a plurality of independent regions into which a repetition of sub-holograms calculated from the same object with different object phases is inscribed alongside and / or one below the other. The observer's eye then averages the different speckle patterns of the individual Fourier transform or Fresnel transform reconstructions of the calculated sub-holograms, whereby the resulting speckle pattern then appears attenuated.

On a holographic display with a viewer window, whose principle in the DE 103 53 439 A1 The applicant is described and this is the basis of this invention, this method is not applicable. Here, a complex-valued light distribution of the diffraction image of an object, eg a 3D scene, is calculated in the observer window. For this purpose, transformations are made of individual object planes into which the 3D scene is virtually cut, and summed up in the viewer window. The transformations correspond to the optical light propagation between the cut object planes and the plane with the observer window. This method results in each object point being associated with a limited localized area on a screen in which the information for the reconstruction of that point is inscribed. This is necessary for a correct reconstruction from the viewer window. On the other hand, encoding different sub-holograms calculated from the 3D scene next to and / or one below the other on the screen according to the prior art would entail that the hologram values associated with an object point are also repeated in different areas on the screen. This is not compatible with the visualization of the reconstructed 3D scene from the viewer window. A general disadvantage of a spatial repetition of partial holograms is also that, given a carrier medium, its resolution for each individual sub-hologram is reduced.

From the WO 2006/119 920 A1 For example, a device for holographic reconstruction of three-dimensional scenes is known, which has optical focusing means which directs, via a spatial light modulator encoded with holographic information, sufficiently coherent light from illuminants to the eyes of at least one observer.

From the WO 95/208 11 A1 Inter alia, it is described that several mutually incoherent lasers are suitable for reducing speckle patterns.

In the DE 197 04 741 A1 is described a holographic screen for large-screen representations, in which even in its manufacture by superposition of multiple diffraction structures in the screen itself a speckle suppression is achieved, the holographic screen has a flat 2D structure.

In the scientific article "Speckle-reduced three-dimensional volume holographic display by use of integral imaging", Seung-Ho Shin and Bahram Javidi, APPLIED OPTICS, Vol. 41, 10.05.2002, no. 14, pp. 2644-2649. ISSN 0003-6935, It is described that in a 3D projection system, speckle patterns are reduced using a rotating diffuser.

The object of the invention is to significantly reduce in a holographic display device with a virtual viewer window the speckle patterns occurring in the reconstruction of a 3D scene and to provide a process operating close to real time in which a carrier medium with a conventional refresh rate can be used.

This object is achieved by the method according to claim 1. Advantageous developments are specified in the dependent claims. The invention is generally based on a method in which a controllable light modulator, in which a hologram of a 3D scene is coded, is illuminated by sufficiently coherent light, in which a reconstruction optic transforms modulated light into a viewer window or an eye position of a viewer's room and in FIG a reconstructed space reconstructs the 3D scene, and in which the illumination is controlled by a control means. The observer window on which the invention is based for reconstructing the 3D scene can here also be set equal to the eye position as the location in the observer's room at which different light distributions of the complex-valued wavefronts of the encoded hologram are generated. In order to see the reconstructed 3D scene, the eyes of an observer must be in this eye position.

On the basis of this method, the object is achieved according to the invention in that the control means influences the coherent light in at least one property such that a plurality of different-wavelength complex-valued wavefronts pass the light modulator, being modulated with the encoded hologram values, and the modulated complex-valued ones Wavefronts are transformed by the reconstruction optics into the eye position and in the reconstruction space at the same location several reconstructions of the 3D scene with mutually slightly different speckle patterns generated (s), which averaged from the eye position as a single speckle-reduced reconstruction of the 3D scene become. By influencing the wavelength of the light, it is advantageously possible to generate a plurality of mutually slightly modified reconstructions of the same 3D scene with mutually slightly altered speckle patterns.

• – ein vom Steuermittel gesteuertes Beleuchtungsmittel generiert eine zeitlich schnelle Folge von Lichtpulsen zum Beleuchten der Rekonstruktionsoptik und des Lichtmodulators, wobei sich die Lichtpulse in ihren Wellenlängen geringfügig voneinander unterscheiden,
• – die zeitlich schnelle Folge von Lichtpulsen passiert den Lichtmodulator, wobei die komplexwertigen Wellenfronten der Lichtpulse mit den kodierten Hologrammwerten moduliert werden, und
• – die zeitlich schnelle Folge der modulierten komplexwertigen Wellenfronten wird in die Augenposition des Betrachterraums transformiert und erzeugt mehrere Rekonstruktionen der gleichen 3D-Szene in zeitlich schneller Folge am gleichen Ort im Rekonstruktionsraum.

For this purpose, the following method steps are carried out in the embodiment of the method according to claim 2:

• An illumination means controlled by the control means generates a temporally fast sequence of light pulses for illuminating the reconstruction optics and the light modulator, the light pulses differing slightly in their wavelengths,
• The temporally fast sequence of light pulses passes through the light modulator, whereby the complex valued wavefronts of the light pulses are modulated with the coded hologram values, and
• The temporally fast sequence of the modulated complex-valued wavefronts is transformed into the eye position of the viewer's space and generates several reconstructions of the same 3D scene in temporally rapid succession at the same location in the reconstruction space.

• – mehrere Beleuchtungsmittel strahlen gleichzeitig kohärentes Licht aus, das vom Steuermittel so beeinflusst wird, dass mehrere kompplexwertige Wellenfronten mit zueinander geringfügig unterschiedlichen Wellenlängen gleichzeitig die Rekonstruktionsoptik und den Lichtmodulator beleuchten,
• – die zueinander geringfügig unterschiedliche Wellenlängen aufweisenden komplexwertigen Wellenfronten passieren den Lichtmodulator gleichzeitig, wobei sie mit den kodierten Hologrammwerten moduliert werden, und
• – mehrere modulierte Wellenfronten werden gleichzeitig in die Augenposition des Betrachterraums transformiert und erzeugen und überlagern gleichzeitig die verschiedenen Rekonstruktionen der gleichen 3D-Szene am gleichen Ort im Rekonstruktionsraum. Dabei werden vorteilhaft Laser als Beleuchtungsmittel verwendet, die in einem räumlichen Verbund so angeordnet sind, dass das kohärente Licht jeweils eines Beleuchtungsmittels mit einer separaten Abbildungsoptik eines Abbildungsmittels in jeweils eine separate Lichtleitfaser abgebildet wird und anschließend in einer einzigen Lichtleitfaser zum gleichzeitigen Beleuchten der Rekonstruktionsoptik und des Lichtmodulators zusammengeführt wird. Damit wird in einfacher Weise ein Beleuchtungsmittel geschaffen, das kohärentes Licht mit zueinander geringfügig unterschiedlichen Wellenlängen zum gleichzeitigen Beleuchten des Lichtmodulators realisiert. Die erfindungsgemäßen Verfahren können für jeweils ein rechtes und ein linkes Auge eines Betrachters separat, zum Beispiel zeitlich nacheinander, durchgeführt werden.

The method can be carried out in a further embodiment of the invention according to claim 3 also by the following other method steps to obtain the same result:

• A plurality of illumination means simultaneously emit coherent light which is influenced by the control means in such a way that a plurality of complex-valued wavefronts with mutually different wavelengths illuminate simultaneously the reconstruction optics and the light modulator,
• The complex-valued wavefronts having slightly different wavelengths pass through the light modulator simultaneously, being modulated with the coded hologram values, and
• - Multiple modulated wavefronts are simultaneously transformed into the eye position of the viewer's space and simultaneously generate and overlay the various reconstructions of the same 3D scene at the same location in the reconstruction space. In this case, lasers are advantageously used as illumination means which are arranged in a spatial arrangement so that the coherent light of a respective illumination means with a separate imaging optics of an imaging agent is imaged in each case a separate optical fiber and then in a single optical fiber for simultaneously illuminating the reconstruction optics and the Light modulator is merged. In this way, a lighting means is created in a simple manner, which realizes coherent light with mutually slightly different wavelengths for the simultaneous illumination of the light modulator. The methods according to the invention can be carried out separately for each of a right and a left eye of a viewer, for example in chronological succession.

The different wavelengths in said methods are determined by the control means Defined changed to each other or exposed within predetermined limits of a random fluctuation.

• – ein Beleuchtungsmittel, das in zeitlich schneller Folge kohärente Lichtpulse aussendet, deren Wellenlängen sich geringfügig voneinander unterscheiden, zum Beleuchten einer Rekonstruktionsoptik und eines Lichtmodulators,
• – eine Rekonstruktionsoptik zum Transformieren einer zeitlich schnellen Folge von modulierten komplexwertigen Wellenfronten in eine Augenposition in einem Betrachterraum und zum Erzeugen mehrerer Rekonstruktionen der gleichen 3D-Szene in zeitlich schneller Folge am gleichen Ort in einem Rekonstruktionsraum,
• – ein Kodiermittel in Form eines Lichtmodulators, in den ein Hologramm einer 3D-Szene kodiert ist, und
• – ein Steuermittel zum Steuern des Beleuchtungsmittels, des Kodiermittels und der Rekonstruktionsoptik.

A holographic display device according to claim 6 serves for carrying out the method according to claim 2 and contains in the light direction the following means:

• An illumination means which emits coherent light pulses whose wavelengths are slightly different from each other in temporally rapid succession, for illuminating a reconstruction optics and a light modulator,
• A reconstruction optical system for transforming a temporally fast sequence of modulated complex-valued wavefronts into an eye position in a viewer space and for producing a plurality of reconstructions of the same 3D scene in temporally fast sequence at the same location in a reconstruction space,
• A coding means in the form of a light modulator into which a hologram of a 3D scene is coded, and
• A control means for controlling the illumination means, the coding means and the reconstruction optics.

• – mehrere, gleichzeitig kohärentes Licht aussendende Beleuchtungsmittel, deren Wellenlängen sich geringfügig voneinander unterscheiden, zum gleichzeitigen Beleuchten einer Rekonstruktionsoptik und eines Lichtmodulators,
• – eine Rekonstruktionsoptik zum gleichzeitigen Transformieren mehrerer modulierter komplexwertiger Wellenfronten eines Hologramms in eine Augenposition eines Betrachterraums, und zum gleichzeitigen Erzeugen und Überlagern mehrerer Rekonstruktionen der gleichen 3D-Szene am gleichen Ort in einem Rekonstruktionsraum,
• – ein Kodiermittel in Form eines Lichtmodulators, in den das Hologramm der 3D-Szene kodiert ist,
• – ein mehrere, mindestens eindimensional aneinandergrenzend angeordnete Abbildungsoptiken aufweisendes Abbildungsmittel zum Abbilden des kohärenten Lichts der Beleuchtungsmittel in mehrere Lichtleitfasern und
• – ein Steuermittel zum Steuern der Beleuchtungsmittel, des Kodiermittels und der Rekonstruktionsoptik.

Another embodiment of the holographic display device according to the invention contains according to claim 8 for carrying out the method according to claim 3 in the light direction following means:

• A plurality of simultaneously coherent light emitting means whose wavelengths are slightly different from each other for simultaneously illuminating a reconstruction optics and a light modulator,
• A reconstruction optics for simultaneously transforming a plurality of modulated complex-valued wavefronts of a hologram into an eye position of a viewer space, and simultaneously generating and superimposing multiple reconstructions of the same 3D scene at the same location in a reconstruction space,
• A coding means in the form of a light modulator into which the hologram of the 3D scene is coded,
• - A plurality of, at least one dimensionally adjacently arranged imaging optics having imaging means for imaging the coherent light of the illumination means in a plurality of optical fibers and
• A control means for controlling the illumination means, the coding means and the reconstruction optics.

An essential feature of the invention is also that the slight change in the wavelengths is in the range of a few nanometers. Even such a change of the wavelengths to each other is sufficient to produce a plurality of slightly different reconstructions of the same 3D scene with mutually changed speckle patterns in the reconstruction space. The respective eye of the observer averages the speckle patterns from the eye position or observer window and sees only a single speckle-reduced reconstruction of the original 3D scene.

A holographic display device for reducing the speckle pattern is, for example, a holographic display. By appropriate design of the individual display components, in particular the optical, the display can be realized either as a projection display or as a direct-view display. As illumination means, both lasers and LEDs can be used in the various embodiments of the invention. An inherently broadband light source such as an LED can also contribute to the reduction of speckle patterns through its spectrum. However, the laser has the advantages of being approximately a point source of light and capable of delivering higher power.

With the invention, as a further advantage, the hologram is coded only once in contrast to the prior art and does not have to be recalculated several times, resulting in a saving of computing time.

The invention will be described in more detail below with reference to exemplary embodiments. In the accompanying drawings show

1 a schematic plan view of a holographic direct view display in a first embodiment and

2 a schematic plan view of a holographic direct view display in a second embodiment.

In the description of the individual figures, the same designations are used for the same components.

The observer window for reconstructing the 3D scene on which the invention is based here corresponds to the visibility region with an eye position as the location in the observer's room, at which several intensity distributions of the complex-valued wavefronts of the coded hologram having slightly different wavelengths are transformed in temporally rapid succession or at the same time. In order to see the reconstructed 3D scene, one eye each of a viewer must be in this eye position.

In 1 A first possible embodiment of a holographic direct-view display is shown schematically and simplified in plan view. In the light direction, a laser is successively arranged as the illumination means L, and a transformation lens, which follows a pixelized light modulator SLM, as reconstruction optical system RO. In a reconstruction space with a conical cross section between the light modulator SLM and an eye position PE, a reconstruction of a 3D scene is shown. From this eye position PE, which lies in the rear focal plane of the transformation lens, the reconstruction of the 3D scene is completely visible to a viewer's eye. The lighting and thus also the light touched components in the beam path are controlled by a control means CM.

An externally controlled by the control means CM laser illuminates the light modulator SLM and arranged in front of the transformation lens with sufficiently coherent light. The propagation direction of the light is indicated by an arrow. The control means CM causes by very fast turning on and off of the laser, that this generates a temporally fast sequence of coherent light pulses, each pulse corresponds to a complex wavefront and the light pulses have mutually different wavelengths. Schematically, the light pulses are indicated by several intensity curves on the arrow line in 1 shown. The wavelengths of the individual light pulses differ only slightly from each other and can be changed defined by appropriate program specifications in the control means CM or be exposed within predetermined limits of a random fluctuation. It makes sense that the change of the wavelengths in the range of a few nanometers, so that the subsequent reconstructions and the corresponding speckle patterns for the means are not too large differences. In the light modulator SLM, the temporally fast succession of light pulses with the coded hologram values of a 3D scene is modulated and transformed in a temporally fast sequence into the rear focal plane BE of the transformation lens arranged in front of the light modulator SLM, wherein the transformation lens is also the reconstruction optics RO at the same time. The rear focal plane BE of the reconstruction optics RO is located in a viewer's room, in which the eye position PE always lies. The modulated complex-valued wavefronts generate in rapid succession several reconstructions of the same 3D scene with slightly different speckle patterns at the same location in the reconstruction space. From the eye position PE, a viewer's eye sees the reconstructions as a single reconstruction of the averaged speckle pattern 3D scene.

Even if temporally fast sequences of light pulses are generated, the same hologram with conventional image refresh rate can advantageously always be displayed on the light modulator and the hologram calculation must then be performed only with this image refresh rate.

As a further significant advantage results with the embodiment 1 in that, in order to further reduce the occurrence of speckle patterns, the number of reconstructions of the 3D scene can be arbitrarily increased without using additional components.

In 2 A second possible embodiment of a holographic direct-view display is shown schematically and simplified in plan view. In the direction of light, successively arranged as illumination means L1, L2 and L3 are three juxtaposed lasers, as imaging means AM three one-dimensional adjacently arranged imaging optics AO, as reconstruction optics RO a transformation lens followed by a pixelated light modulator SLM provided. Thus, by way of example, three slightly different reconstructions with mutually slightly different speckle patterns for averaging for one eye can be generated. It goes without saying that the number of lasers and corresponding imaging optics can be arbitrarily increased in order to generate a larger number of reconstructions simultaneously and to improve the speckle reduction by averaging. In a reconstruction space with a conical cross section between the light modulator SLM and the eye position PE, the reconstruction of the 3D scene is shown. From the eye position PE, which lies in the rear focal plane of the transformation lens, the reconstruction of the 3D scene for a viewer's eye is completely visible. The lighting and thus also the light touched components in the beam path are controlled by a control means CM.

Programmatically initiated by the control means CM, at the same time, three lasers with mutually slightly different wavelengths emit sufficiently coherent light, which is imaged in, for example, an optical fiber via an associated imaging optical unit AO. Both the laser and the imaging optics AO are arranged one-dimensionally adjacent to one another. With a larger number of lasers, however, they can also be arranged two-dimensionally as a composite. A suitable imaging means for two-dimensional imaging of the two-dimensional composite of lasers is then advantageously designed as a matrix-shaped lens array. The light of the optical fibers is concentrated in a single optical fiber LLF and, under the control of the control means CM, programatically illuminates the transformation lens and the light modulator SLM with combined light having three slightly different wavelengths. The transformation lens transforms the different wavelength light into its rear focal plane BE into the eye position PE. If there is a viewer's eye at this point, then three complex-valued wavefronts with mutually different wavelengths are present simultaneously within the eye pupil, from which the transformation lens simultaneously generates three reconstructions of the 3D scene. Since the three reconstructions with mutually slightly different speckle patterns are created and overlaid simultaneously at the same location in the reconstruction space, the eye averages over these reconstructions and sees only a single reconstruction of the reduced speckle pattern 3D scene.

It may also be in the process 2 a light modulator with conventional refresh rate can be used and advantageously, the hologram calculation will be done only with this frequency.

In the method according to the invention, the Fourier transformation is preferably used, since it can be easily implemented in terms of programming technology and can be realized very precisely by optical systems.

The hologram coding can be used in the embodiments in FIG 1 and 2 can be variably specified so that the reconstructions of the 3D scene in front of and / or behind the screen can be seen. The light modulator SLM also fulfills the function of the screen at the same time.

The position data of a viewer's eye are in 1 and 2 Usually determined by a position detection system, not shown, and taken over by the control means CM, which, however, need not be discussed in detail here.

The method for reducing speckle in the reconstruction of a 3D scene described on the basis of exemplary embodiments of a holographic direct-view display can also be used according to the invention in a holographic projection display.

Claims (12)

Method for reducing speckle of a three-dimensional holographic reconstruction produced in a holographic reproduction device, in which a controllable light modulator (SLM) in which a hologram of a 3D scene is coded is illuminated by sufficiently coherent light, in which a reconstruction optics (RO ) spatially modulated light within a viewer space in an eye position, which (in a back focal plane of the reconstruction optics RO) is transformed and, in a reconstruction space reconstructs the 3D scene, and - in which the lighting of a control means (CM) is controlled, characterized characterized in that the control means (CM) influences the coherent light in at least one property such that a plurality of complex-valued wavefronts having slightly different wavelengths relative to each other within a few nanometers pass through the light modulator (SLM) modulating with coded hologram values rt, and the modulated complex wavefronts are transformed by the reconstruction optics (RO) into the eye position (PE) and in the reconstruction space between the eye position (PE) and the light modulator (SLM) at the same location several reconstructions of the same 3D scene with each other produce different speckle patterns which are seen from the eye position (PE) from the respective eye of the observer averaged as a single speckle reduced reconstruction (RE) of the 3D scene. A method for reducing speckle according to claim 1, wherein An illumination means (L) controlled by the control means (CM) generates a temporally fast sequence of coherent light pulses which differ slightly in their wavelengths in the range of a few nanometers for illuminating the reconstruction optics (RO) and the light modulator (SLM), The time-series of light pulses passes through the light modulator (SLM), the complex-valued wavefronts of the light pulses being modulated with the coded hologram values, and - The temporally fast sequence of the modulated complex wavefronts in the eye position (PE) of the viewer space is transformed and several reconstructions of the same 3D scene in rapid time series at the same location in the reconstruction space are generated. A method of reducing speckle according to claim 1, wherein - a plurality of illumination means (L1, ..., Ln) simultaneously emit coherent light which is controlled by the control means (CM) such that a plurality of complex-valued wavefronts slightly different from each other in the range of a few nanometers Wavelengths simultaneously illuminate the reconstruction optics (RO) and the light modulator (SLM), - the complex-valued wavefronts with slightly different wavelengths passing each other within the range of a few nanometers pass through the light modulator (SLM) simultaneously, being modulated with the coded hologram values, and - several modulated complex-valued waveshapes Wavefronts are simultaneously transformed into the eye position (PE) of the viewer space and multiple reconstructions of the same 3D scene in the same place simultaneously create and spatially overlap in the reconstruction space. A method for reducing speckle according to claim 3, wherein the coherent light of each illuminant (L1, ...; Ln) is directed with separate imaging optics (AO) of an imaging means (AM) into a respective separate optical fiber and then into a single optical fiber Optical fiber (LLF) for illuminating the reconstruction optics (RO) and the light modulator (SLM) is merged. A method for reducing speckle according to claims 2 and 3, wherein the different wavelengths are changed by the control means (CM) defined to each other in a defined manner or subjected to a random fluctuation within predetermined limits. Holographic display device for carrying out the method according to claim 2, characterized in that the following means are provided in the light direction: - an illumination means (L) which emits in rapid time coherent coherent light pulses whose wavelengths are slightly different in the range of a few nanometers, for illumination a reconstruction optics (RO) and a light modulator (SLM), - a reconstruction optics (RO) for transforming a temporally fast sequence of modulated complex wavefronts in an eye position (PE) of a viewer space and generating multiple reconstructions of the same 3D scene in rapid time sequence at the same location in a reconstruction space, - a coding means in the form of a light modulator (SLM), in which a hologram of a 3D scene is coded, and - a control means (CM) for controlling the illumination means (L), the coding means and the reconstruction optics ( RO). Holographic display device according to Claim 6, in which a laser or an LED is optionally provided for illuminating the light modulator (SLM). Holographic display device for carrying out the method according to claim 3, characterized in that the following means are provided in the light direction: - a plurality of simultaneously emitting coherent light means (L1, ...: Ln) whose wavelengths are slightly different in the range of a few nanometers, for simultaneously illuminating a reconstruction optics (RO) and a light modulator (SLM), - reconstruction optics (RO) for simultaneously transforming a plurality of modulated complex valued wavefronts into an eye position (PE) of a viewer space and simultaneously generating and superimposing multiple reconstructions of the same 3D scene on same location in a reconstruction space, - a coding means in the form of a light modulator (SLM), in which a hologram of a 3D scene is encoded, - an imaging means (AM) for imaging, which has a plurality of imaging optics arranged at least one-dimensionally adjacent to one another n of the coherent light of the illumination means (L1, ...: Ln) into a plurality of optical fibers, and - a control means (CM) for controlling the illumination means (L1, ...; Ln), the coding means and the reconstruction optics (RO). A holographic display device according to claim 8, wherein said illumination means (L; L1, ...: Ln) are arranged in a spatial array and simultaneously emit coherent light with wavelengths slightly different to each other in the range of a few nanometers. A holographic display device according to claim 8, wherein the illumination means (L; L1, ...: Ln) are lasers. Holographic display device according to claim 6 and 8, in which the change of the wavelengths takes place in the range of a few nanometers. Holographic display device according to claim 6 and 8, which is designed as a holographic display, in which the optical components can be modified either for a direct-view display or for a projection display.

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